1. Field of the Invention
The present invention relates to a method for the reduction of load cycle oscillations in the drive train of a motor vehicle which includes detecting a change in available torque in the drive train of a motor vehicle, and determining the period of a load cycle oscillation which is caused by a change in the useful torque. The invention also relates to a device for the reduction of load cycle oscillations in the drive train of a motor vehicle.
2. Description of the Related Art
Changing transmission torques occur in drive trains of vehicles in different driving conditions. A change in the driving condition of a vehicle or motor vehicle, for example an acceleration, requires a change in the drive torque generated by the vehicle engine. Since the drive train of a motor vehicle comprises various masses and elasticities, the drive train of the motor vehicle is excited to load cycle oscillations as a result of this torque change or of this load cycle. The load cycle oscillations are caused by resonance, particularly at the lowest characteristic frequency of the system as a whole. This, with the clutch engaged, is the entire drive train from the vehicle engine as far as the drive wheels.
The load cycle oscillations occur typically in driving conditions in which the change of the transmission or drive torque takes place within a very short time. Driving conditions typical of this are, for example, the load change with a clutch closed, a torque jump after synchronization occurs during starting or gear shifting, or else first ignition during the starting of the engine by means of a two-mass flywheel (TMF).
Various solutions have hitherto been taken into consideration in the prior art in order to avoid or reduce the load cycle oscillations.
In a known solution, a particularly slow torque change takes place. In this case, the torque change acting on the drive train per unit time is kept below a predetermined value, so that the amplitude of the oscillation resulting from this torque change also remains low and the damping members present in the drive train can damp these oscillations to a sufficient extent. The disadvantage of this solution, however, is that the vehicle reacts too sluggishly and experiences a considerable loss of dynamics.
DE 195 36 320, which corresponds to GB 2,305,743, has hitherto proposed a stepped torque change. In this case, a desired torque change is detected and, in order to change the useful torque, an actuator is activated in such a way that the torque change takes place in a plurality of steps. The second step commences with a time delay in respect of the first step, so that the various oscillations generated as a result of the stepped torque change cancel one another out due to destructive interference. In this known method, however, there is the problem that the stepped torque changes usually cannot be controlled very accurately. The same also applies to clutch actuators in which the transmission torque profile is controlled. Furthermore, systems of this kind are mostly unavailable or can be implemented only at a particularly high outlay in design terms.